An active matrix display device, such as an active-matrix organic light-emitting display panel, has a two-dimensional pixel array comprising a plurality of pixel rows. Each of the pixel rows has a plurality of pixels arranged in the x direction, as shown in FIG. 1. These pixel rows are arranged as lines in the y direction so that they can be sequentially driven by a plurality of scanning signals provided by the scanning lines in one or more scanning circuits. In FIG. 1, the display panel 1 has a plurality of color pixels 10 arranged in a two-dimensional array.
In a color organic light-emitting display panel, each color pixel 10 generally comprises three color sub-pixels R, G, B for emitting red, green and blue colors, respectively, as shown in FIG. 2. The color sub-pixels R, G, B comprise three different organic light-emitting devices 24, 25 and 26 in a diode form. Organic light-emitting diodes (OLEDs) are known in the art. For example, the red organic light-emitting device 24 is an organic electroluminescent device having a plurality of organic layers disposed between a cathode layer 150 and an anode layer 110 formed on a substrate 100, as shown in FIG. 3. The organic layers in the organic layer section consist of a hole injection layer (HIL) 120, a hole transport layer (HTL) 122, an emissive layer (EML) 130, and an electron transport layer (ETL) 140. The green and blue organic light-emitting devices 25 and 26 are structurally similar to the layer structure as shown in FIG. 3, except that each of the organic light-emitting devices 24, 25 and 26 comprises a different light emitting material in the EML layer so that each device emits a different color spectrum. In FIG. 3, the thickness of the organic layer section, L, serves as a resonant cavity in an OLED.
Each of color spectra has a different spectral peak expressed by the coordinates in a CIE color space. For example, a red color spectrum can be represented by CIEx: 0.682 color coordinate. It is desirable to produce an organic light emitting display wherein the CIE coordinates can be controlled.